Field of the Invention
The invention relates to a pressure sensor component having a semiconductor chip with an integrated pressure sensor carried on a chip carrier. A pressure-detecting surface is subjected to the pressure to be measured. The assembly is encapsulated in a device encapsulation made from an electrically insulating material and surrounding at least partially the semiconductor chip and/or the chip carrier as well as the bond wires which connected outwardly guided electrode terminals and the pressure sensor and/or the electronic circuit of the semiconductor chip. The chip carrier has electrode terminals electrically connected to the pressure sensor and/or an electronic circuit, assigned to the pressure sensor, of the semiconductor chip. The electrode terminals penetrate the device encapsulation. At least that portion of the device encapsulation which is adjacent the pressure-detecting surface of the pressure sensor is formed by a homogeneous pressure-transmitting medium comprising an enveloping compound, which transmits the pressure to be measured substantially without delay and attenuation but is mechanically resistant. The material is substantially dimensionally stable, at least after curing, as appropriate. The pressure to be measured is guided directly by the enveloping compound onto the pressure-detecting surface of the semiconductor chip, and the pressure sensor and/or the pressure sensor component is covered tightly on all sides against mechanical and/or chemical influences. The method further pertains to a method of producing such a pressure sensor component.
Pressures are measured by bringing the medium to be measured up to the sensor, or by transmitting the pressure prevailing in the medium to the sensor. On the other hand, the application of a semiconductor pressure sensor in the final use requires that the sensor chip is provided with a protective encapsulation by being covered with a suitable material, normally plastic. The covering or encapsulation of the sensor chip requires several process steps wherein the device is given its final form and an electric connecting cable is encapsulated by injection molding after soldering to the printed circuit board.
The semiconductor chip, usually a silicon base material chip, is generally provided in a rigid housing, for example DIP housing (dual inline package housing), SMD housing (surface mounted design housing), or in special designs. The housing is subsequently fitted on a printed circuit board. In one prior art system, the pressure is coupled in via a diaphragm which covers, and thus protects, the sensitive sensor. The diaphragm consists of metal or plastic and also can be designed as a separate additional assembly. Problems frequently arise in this case because pressure is only insufficiently coupled in through the housing up to the sensor chip with the sensor being simultaneously protected. Generally, what is required is a tight connection between the medium to be measured and the sensor which is easy to produce in order to avoid extraneous air which falsifies the pressure measurement from flowing in. On the other hand, in many cases there is, moreover, a requirement to separate the medium to be measured from the metal constituents of the sensor and from the semiconductor chip, in order to avoid the risk of corrosion or destructive influence by the medium on the sensitive constituents of the sensor. Other designs of known pressure sensor components provide an open housing in which the protection of the sensor chip against environmental influences is regarded only as a problem of secondary importance and the sensor chip is not protected. Such designs are generally not suitable for non-aggressive media.
A pressure sensor component as it is described above is disclosed German published, non-prosecuted application DE 42 38 113 A1. There, the semiconductor chip is surrounded on all sides by an elastic material (silicone rubber) which simultaneously serves to fasten and cover the chip. The configuration, comprising semiconductor chip and silicone rubber covering, is encapsulated in a conventional housing made from plastic material.
A conventional type of semiconductor pressure pick-up is disclosed in German published, non-prosecuted application DE 42 03 832 A1.
A pressure sensor component with a relatively thick diaphragm structure is disclosed by David J. Beebe et al. in Sensors and Actuators, Vol. A 50, 1995, p. 55-65. The applied pressure force is directed to the diaphragm via a dome-like solid body structure.
Finally, the use of polyimide resin compounds to encapsulate semiconductor components has been disclosed in German published, non-prosecuted application DE 40 06 450 A1.
It is common to all of the prior art designs of semiconductor pressure sensors that their manufacture requires a multistage process for covering or encapsulating the device and for forming the component into its desired component structure.